Catalyst for hydrocracking and method for catalytic hydrodewaxing of gas oil

ABSTRACT

The invention relates to a new catalyst applicable in hydrocracking of hydrocarbons. The catalyst contains as catalytically active components: a) a ZSM-5 zeolite wherein 10-100% of the exchangeable hydrogen ions have been replaced by nickel ions, and b) 0.3-3 parts by weight of magadiite in hydrogen form for 1 part by weight of component (a). The catalyst can be applied in hydrodewaxing of gas oil, and enables the production with an extremely low pour point.

BACKGROUND OF THE INVENTION

This Application is a 371 of PCT/HU96100077, filed Dec. 16, 1996 whichis based on Hungarian Application P9603093, filed Nov. 08, 1996.

The invention relates to a new catalyst applicable in hydrocracking ofhydrocarbons. More particularly, the invention relates to a catalystcomprising as active components ZSM-5 zeolite which has been subjectedto ion exchange with nickel and magadiite in hydrogen form (further on:Ni-ZSM-5/H-magadiite catalyst). This catalyst can be applied toparticular advantage in hydrodewaxing of gas oil, and possesses highselectivity and a long life time.

The invention also relates to a method for producing arctic gas oil(i.e. gas oil with extremely low pour point) by subjecting gas oil tohydrodewaxing in the presence of the above catalyst.

It has been known for a long time that pour point of gas oils can belowered by reducing the amount of higher straight-chained and moderatelybranched--with only single methyl groups in side chains--paraffins(further on: n-paraffins) contained therein. One of the methods suitablefor reducing the amount of n-paraffins in gas oils is cracking in thepresence of hydrogen and a catalyst, i.e. catalytic hydrocracking(hydrodewaxing) of gas oils. For this purpose, those catalysts(so-called shape-selective catalysts) are particularly suitable whichcatalyse only the cracking of higher n-paraffins intended to be removed,but do not or only slightly catalyse the cracking of other components(such as isoparaffins, lower hydrocarbons, etc ). Such shape-selectivecatalysts have been disclosed, inter alia, in U.S. Pat. Nos. 3,700,585and 3,894,934. A very widely used representative of shape-selectivecatalysts is the commercially available ZSM-5 zeolite catalyst inhydrogen form (ZSM-5 or, according to a more accurate terminology,H-ZSM-5) Utilizing such catalysts, pour point of gas oils can be loweredtypically to -5 to -25° C., depending on the pour point of the startingsubstance. Hydrogen gas present at cracking does not participate in thereaction, and its role is only to suppress further dehydrogenation ofolefins with a single unsaturated bond, which are one of the primaryproducts of cracking This further dehydrogenation of olefins proceedsupon thermal effects, and leads to coke-formation on the catalyst,decreasing (in extreme cases even breaking down) thereby the activity ofthe catalyst. It is, however, obvious that further dehydrogenation ofolefins with a single unsaturated bond can be suppressed only to anextent determined by the reaction equilibria under the prevailingconditions and by the law of mass action.

A smaller fraction of olefins with a single unsaturated bond, which formas primary products in hydrocacking, consists of lower hydrocarbonswhich appear in gasoline (a twin product of hydrocracking). Thesecompounds have a favourable influence on the quality of gasolineHowever, the situation is different with higher olefins having a singleunsaturated bond which appear in gas oil. Hydrogen present in theprocess only suppresses but does not prevent the thermal dehydrogenationof these latter olefins. A part of the resulting olefins with multipleunsaturated bonds adsorbs on the surface of the catalyst and gets cokedthere, whereas another part of them gets stabilized by conversion intoaromatics. The resulting aromatics decrease the cetane number of gas oiland lead to an increase in noise level when gas oil is used in engines.

A method for suppressing these latter disadvantages has been disclosedin Hungarian Patent No. 209,141. According to this method, gas oil issubjected to hydrodewaxing in the presence of a catalyst comprising asactive components ZSM-5 zeolite which has been subjected to ion exchangewith nickel, and magadiite which has been subjected to ion exchange withnickel (Ni-ZSM-5/Ni-magadiite catalyst). This catalyst is able tosuppress the formation of aromatics from olefins with multipleunsaturated bonds, whereby both the decrease in cetane number and theincrease in noise level upon use in engines can be suppressedconsiderably, without affecting, however, the level of n-paraffinremoval and thereby the pour point of the resulting gas oil.

However, with the increase of motorisation, there is an increasing needfor gas oils with extremely low pour point, typically about or below-50° C., the production of which has not yet been solved.

SUMMARY OF THE INVENTION

Now we have found that when a catalyst comprising as active componentsZSM-5 zeolite, which has been subjected to ion exchange with nickel, andmagadiite in hydrogen form (i.e. Ni-ZSM-5/H-magadiite catalyst) isapplied in the otherwise known catalytic hydrodewaxing of gas oil, a gasoil with extremely low pour point is obtained. The resulting gas oil canbe safely used even under arctic conditions, without, however, affectingconsiderably either the cetane number of gas oil or the noise level whengas oil is used in an engine.

Additional features and advantages of the present invention aredescribed in, and will be apparent from, the detailed description of thepresently preferred enbodiments.

DETAILED DESCRIPTION OF THE PRESENTLY PREFERRED EMBODIMENTS

The present invention provides a catalyst for hydrocracking ofhydrocarbons. Specifically, the catalyst of the present inventionincludes an Ni-ZSM-5 zeolite and a magadiite in hydrogen form. Theinventors have discovered that the use of such a catalyst made pursuantto the present invention enables the production of a gas oil withextremely low pour point. Moreover, the product obtained with thecatalyst of the present invention can even be utilized under arcticconditions, without considerably affecting either the cetane number ofgas oil or the noise level when gas oil is used in an engine.

Thus, the invention relates to a catalyst suitable for hydrocrackinghydrocarbons, particularly for hydrodewaxing gas oils. The catalystaccording to the invention comprises as active components

(a) ZSM-5 zeolite, which has been subject ad to ion exchange with nickel(Ni-ZSM-5) and

(b) magadiite in hydrogen form (H-magadiite).

In Ni-ZSM-5, the one of the catalytically active components of thecatalyst according to the invention, 10-100%, preferably 30-100%, morepreferably 50-100%, particularly preferably 80-100%, of the exchangeablehydrogen ions of ZSM-5 zeolite in hydrogen form (H-ZSM-5) have beenreplaced by nickel ions

The catalyst according to the invention comprises, for 1 part by weightof Ni-ZSM-5 with the above nickel replacement level, 0.3-3 parts byweight, preferably 0.5-2 parts by weight, particularly preferably0.75-1.5 parts by weight, of H-magadiite.

The catalyst according to the invention may optionally also containinert binders and/or auxiliary agents necessary for preparing a shapedcatalyst. As binders and/or auxiliary agents, any substance known to beapplicable for this purpose can be used, examples of which are waterglass, phosphates and hydrated aluminum oxides. The amount of bindersand/or auxiliary agents may be 1-95% by weight, usually 5-50% by weight,preferably 10-30% by weight, related to the total weight of thecatalyst. It is, however, not absolutely necessary to use any binder orauxiliary agent, since the catalyst can also be applied as a powdermixture or in a form compressed without any binder.

We have found that using the above catalyst a gas oil with much lowerpour point than usual, but at the same time with good cetane number andcausing low noise level when used in an engine, can be produced. Thisobservation is very surprising from many respect. Although fromHungarian patent No. 209 141, which discloses the use of aNi-ZSM-5/Ni-magadiite catalyst, one could conclude that the presence ofa magadiite component will suppress the cyclization of multiplyunsaturated olefins, avoiding thereby a lowering in cetane number and anincrease in noise level, but it could by no means be expected that theH-magadiite component will considerably increase the n-paraffin crackingactivity of the catalyst. Since when one proceeds as disclosed inHungarian patent No. 209,141, the n-paraffin content of the gas oilproduct (and its pour point closely connected therewith) is hardlychanged as compared to that attainable by a method utilizing H-ZSM-5catalyst alone. From a combination of the teachings of Hungarian patentNo. 209,141 and U.S. Pat. Nos. 3,700,58 and 3,894,934, one skilled inthe art could rather conclude that the magadiite component will suppresscyclization of multiply unsaturated olefins without, however, exertingany essential influence on the cracking of n-paraffins. Consequently,one could not expect that an arctic gas oil with a pour point of about-50° C. will form. A likewise unexpected observation is that thecatalyst according to the invention has a longer life time than thecatalyst disclosed in Hungarian Patent No. 209,141. Taking into accountthat coke formation is caused by multiply unsaturated olefins, and theintroduction of Ni ions assists their partial rehydrogenation, one hadto expect that the catalyst according to the invention, in which onlyone of the components comprises Ni-ions, will be less able to eliminatethe formation of coke-forming compounds. Our practical experiences are,however, fully contrasted with this expectation. Without wishing tobound the essence of the invention to theoretical considerations, weassume that the favourable effects observed with the catalyst accordingto the invention (considerable increase in cracking of n-paraffins,prolonged life time of the catalyst) can be traced back to some specificfavourable structural characteristics defined by the acidic centres ofH-magadiite

Ni-ZSM-5 zeolite, which is one of the active components of the catalystaccording to the invention, can be prepared by, a known ion exchangeprocess from commercially available Ni-ZSM-5 zeolite in H-form. Ionexchange can be performed (e.g. as disclosed in Hungarian patent No.209,141).

H-magadiite, the second active component of the catalyst according tothe invention, is a commercially available material, which can also beprepared by known methods [see R. K. ller: J. Colloid Sci. 19, 648-657(1964) and G. Lagaly et al.: Proc. Int. Clay Conf. Madrid, 1973,663-673]. H-magadiite can also be prepared from magadiite withexchangeable cations other than hydrogen by a known ion exchange method(acidic treatment):

The catalyst according to the invention can be prepared by simplyadmixing the two active components. However, when a shaped catalyst withappropriate deformation stability is required, the two active componentsare admixed with conventional binders and/or auxiliary agents, theresulting mixture is granulated, and the granules are dried, ifnecessary.

When used for hydrodewaxing of gas oil, the above catalyst is calcinedfirst in a known way (e.g. as described in Hungarian Patent No.209,141), and then it is subjected to heat treatment in hydrogen or in ahydrogen-containing gas mixture, such as in reforming gas. This seriesof operation is termed here as "activation of the catalyst". Calcinationis performed typically at 500-600° C. for 1-3 hours. Treatment withhydrogen is performed generally at a slightly lower temperature (e.g. at400-550° C.) for 1-3 hours. gas oil is hydrodewaxed with thethus-activated catalyst under conditions disclosed in detail in theliterature. The operational parameters may be e.g. the following:

reactor temperature: 300-500° C.

spatial velocity (LHSV): 1-2 h⁻¹

gas/liquid ratio: 500-1000 Nm³ /m³

pressure: 30-50 bar

The following non-limiting Examples serve to illustrate further detailsof the invention.

EXAMPLE 1

Preparation of the Catalyst 4300 g of Ni-ZSM-5, wherein 50% of theexchangeable hydrogen ions had been replaced by nickel ions, 3200 g ofH-magadiite. 4.2 litres of ethyl silicate (SiO₂ content: 31-32%), 900 gof 65 w/w % H₃ PO₄ 3 liters of water and 250 g of Al(OH)₃ were mixed,the resulting mass was granulated, and the granules were dried at 120°C.

EXAMPLE 2

Hydrodewaxing of Gas Oil with the Catalyst According to the Invention

Prior to use, 100 ml of the catalyst obtained according to Example 1were calcined in the reactor at 550° C. for 2 hours, 3and then areforming gas with a hydrogen content of 80 v/v % was passed through thecatalyst at a rate of 100 l/hour for 12 hours under a pressure of 40bar. Thereafter, hydrodewaxing of a gas oil (a 1:1 v/v mixture ofRussian heavy gas oil and vacuum gas oil, its characteristics are listedin Table 1) was started under the following conditions:

reactor temperature: 340-430° C.

spatial velocity: 1.5 h⁻¹

gas/liquid ratio: 700 Nm³ /m³

pressure 40 bar

H₂ content of reforming gas: 80 v/v %

The resulting product was distilled to remove gasoline fraction, and thecharacteristics of the resulting gas oil were determined. The resultsare given in Table 1.

EXAMPLE 3

Hydrodewaxing of Gas Oil with a Comparative Catalyst

For comparison purposes, the process described in Example 2 was repeatedusing a Ni-ZSM-5/Ni-magadiite catalyst prepared according to Example 1of Hungarian patent No. 209,141. The results are given in Table

                  TABLE 1                                                         ______________________________________                                        Characteristics of the starting substance and of the hydrodewaxed gas         oils                                                                                                      Hydrodewaxed                                                        Starting  gas oil product                                   Characteristics   substance Ex. 2    Ex. 3                                    ______________________________________                                        Density, kg/m.sup.3                                                                             867       887      877                                      Sulphur content, %                                                                              0,905     1,05     0,98                                     Nitrogen content, ppm                                                                           230       235      233                                      Basic nitrogen content, ppm                                                                     129       138      134                                      Viscosity at 20° C., cSt                                                                 10,66     13,74    13,16                                    Pour point, ° C. (ASTM D 2500)                                                           0         -52      -18                                      Cetane index      56        52       52                                       Flash point, ° C.                                                                        88        96       96                                       Saturated compounds, w/w %                                                                      63,4      56,3     53,42                                    of them: n-paraffins, w/w %                                                                     27        8,47     12,42                                    Aromatics, w/w %  36,60     43,70    46,60                                    ______________________________________                                    

It appears from the data of Table 1 that when using the catalystaccording to the invention a gas oil with extremely low pour point (-52°C.), usable even under arctic conditions, can be obtained. Whereas thepour point of the product obtained with the closest known catalyst isonly -18° C. At the same time, the product obtained with the catalystaccording to the invention retains the favourable properties of theproduct prepared according to the closest known solution: its aromaticscontent and cetane index are essentially the same as those of theproduct obtained according to the comparative example.

When operating as described in Example 3 the activity of the catalystdecreased after 840 hours of operation to such an extent thatrefreshment was required (regeneration of the catalyst was, however, notyet necessary). Refreshment was performed by passing reforming gasthrough the catalyst for 12 hours at 500° C. In contrast, no refreshmentof the catalyst according to the invention was required during the wholeperiod of operation (1100 hours); the activity of the catalyst remainedpractically unchanged at the end of the 1100th hour. After 1100 hours ofoperation the reaction according to Example 2 was stopped, the catalystwas removed from the reactor, and its coke content was determined. 4.4w/w % of coke visa deposited on the catalyst. As an information, in suchreactions, catalysts require regeneration generally when 12-14 w/w % ofcoke has been deposited thereon.

It is understood that certain modifications and changes to the preferredembodiments described herein will be apparent to those skilled in theart. Such changes and modifications can be made without departing fromthe spirit and scope of the present invention and without diminishingit, intended advantages. Therefore, the appended claims are intended tocover such changes and modifications.

What we claim is:
 1. A catalyst for hydrocracking of hydrocarbons, thecatalyst comprising:(a) an Ni-ZSM-5 zeolite, wherein 10 to 100% of theexchangeable hydrogen ions have been replaced by nickel ions, and (b) amagadiite in hydrogen form, wherein 0.3 to 3 parts by weight of themagadiite is present for 1 part by weight of the Ni-ZSM-5 zeolite. 2.The catalyst of claim 1 wherein 50 to 100% of the exchangeable hydrogenions have been replaced by nickel ions.
 3. The catalyst of claim 1wherein 0.5 to 2 parts by weight of the magadiite is present for 1 partby weight of the Ni-ZSM-5 zeolite.
 4. The catalyst of claim 1 wherein0.75 to 1.5 parts by weight of the magadiite is present for 1 part byweight of the Ni-ZSM-5 zeolite.
 5. The catalyst of claim 1 furthercomprising a binder in an amount of 1 to 95 w/w % for the total weightof the catalyst.
 6. The catalyst of claim 5 wherein the binder ispresent in an amount of 5 to 50 w/w % for the total weight of thecatalyst.
 7. The catalyst of claim 1 further comprising an auxiliaryagent in an amount of 1 to 95 w/w % for the total weight of thecatalyst.
 8. The catalyst of claim 7 wherein the auxiliary agent ispresent in an amount of 5 to 50 w/w % for the total weight of thecatalyst.
 9. A method for catalytic hydrodewaxing of gas oil, theprocess comprising the step of:hydrocracking a gas oil in the presenceof a catalyst, the catalyst comprising:(a) an Ni-ZSM-5 zeolite, wherein10 to 100% of the exchangeable hydrogen ions have been replaced bynickel ions, and (b) a magadiite in hydrogen form, wherein 0.3 to 3parts by weight of the magadiite is present for 1 part by weight of theNi-ZSM-5 zeolite.
 10. The method of claim 9 wherein 50 to 100% of theexchangeable hydrogen ions in the Ni-ZSM-5 zeolite have been replaced bynickel ions.
 11. The method of claim 9 wherein 0.5 to 2 parts by weightof the magadiite is present for 1 part by weight of the Ni-ZSM-5zeolite.
 12. The method of claim 9 wherein 0.75 to 1.5 parts by weightof the magadiite is present for 1 part by weight of the Ni-ZSM-5zeolite.
 13. The method of claim 9 wherein the catalyst furthercomprises a binder in an amount of 1 to 95 w/w % for the total weight ofthe catalyst.
 14. The method of claim 13 wherein the binder is presentin an amount of 5 to 50 w/w % for the total weight of the catalyst. 15.The method of claim 9 wherein the catalyst further comprises anauxiliary agent in an amount of 1 to 95 w/w % for the total weight ofthe catalyst.
 16. The method of claim 15 wherein the auxiliary agent ispresent in an amount of 5 to 50 w/w % for the total weight of thecatalyst.